Question

我正在尝试将一些数据放入listview，但我有这个错误：

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference

我认为这是我的适配器需要修复。

感谢您的帮助！

这是我的活动：

package com.example.taypaygay;

import java.util.jar.Attributes.Name;

import com.example.taypaygay.*;
import android.app.Activity;
import android.os.Bundle;
import android.widget.Button;
import android.widget.ListView;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.TextView;

public class Horaires extends Activity implements OnClickListener 
{
private String activityName = "Horaires";
private TextView textviewDeparts;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_horaires);
    ((Button)findViewById(R.id.buttonretour)).setOnClickListener(this);

    ListView listView = (ListView)findViewById(R.id.listView);

    textviewDeparts = (TextView)this.findViewById(R.id.departs);
    ThreadStopName threadname = new ThreadStopName(listView, this);
    threadname.execute(textviewDeparts);
}

@Override
public void onClick(View v) {
    if (v.getId() == R.id.buttonretour)
    {
        finish();
    }

}

/*private void print(String str)
{
    textviewDeparts.setText(textviewDeparts.getText() + "\n" + str);
}*/


}

这是“ThreadStopName”

package com.example.taypaygay;
import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URI;
import java.net.URL;
import java.sql.Connection;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.conn.DefaultClientConnection;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

import android.app.Activity;
import android.content.Context;
import android.os.AsyncTask;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;


public class ThreadStopName extends AsyncTask<TextView, String, String>{

public InputStream stream;
public TextView textView;
public static String Name;
public ListView list2;
private Activity context;

 public ThreadStopName(ListView list, Activity context)
{this.list2 = list;
this.context = context;}

public ListView listView;

public void parseXML()
{
    try {
        URI url=null;
        url = new URI(MainActivity.QueryStop);


    // open the file
        try {
            HttpClient client = new DefaultHttpClient();
            HttpResponse response = client.execute(new HttpGet(url));

            stream = response.getEntity().getContent();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            publishProgress("Exception: " + e.toString());
        }

    //  print(">Input stream");
      DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
      dbf.setIgnoringComments(true);
      dbf.setIgnoringElementContentWhitespace(true);
      // NOTE: not valid on Android
      //dbf.setValidating(true);
      DocumentBuilder db = dbf.newDocumentBuilder();
      // start parsing the file
      Document doc = db.parse(stream);
      // normalize the content
      doc.getDocumentElement().normalize();

     // this.print("Root element " + doc.getDocumentElement().getNodeName());

      // get the pointer to all the users
      NodeList stopList = doc.getElementsByTagName("stopName");

      String Name="";



      List<String> contentArray = new ArrayList<String>();

      for (int i = 0; i < stopList.getLength(); i++)
      {
          Element elementStopCode = (Element)stopList.item(i);
          String strName = elementStopCode.getTextContent();
          contentArray.add(elementStopCode.getTextContent());
          Name = Name.concat("\n"+ strName);     
      }

      ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(context, R.layout.simplerow, contentArray);
      listView.setAdapter(arrayAdapter);

      publishProgress(Name);

        /*Node name = userContent.item(1);
        Element elName = (Element)name;*/
        // get the attribute
        //String attribute = user.getAttributes().item(0).getTextContent();
    }
  catch (Exception e) 
  {
    e.printStackTrace();
    publishProgress("Exception: " + e.toString());
    //this.print("Exception " + e.toString());
  }

}


@Override
protected String doInBackground(TextView... params) {
    textView = params[0];
    parseXML();
    return null;
}

protected void onProgressUpdate(String...p)
{
    String message = p[0];
    textView.setText(message);
}

}

这是我的“activity_horaires.xml”：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:gravity="center_vertical"
tools:context="com.example.tpgcapese.Activity2" >

<TextView
    android:id="@+id/Horaire"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignParentTop="true"
    android:layout_centerHorizontal="true"
    android:layout_marginTop="22dp"
    android:text="Arrêts à 500m"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textSize="30sp"
    android:textStyle="bold" />

<Button
    android:id="@+id/buttonretour"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_alignParentBottom="true"
    android:layout_centerHorizontal="true"
    android:layout_marginBottom="20dp"
    android:text="Retour"
    android:textSize="20sp"
    android:textStyle="bold" />

<TextView
    android:id="@+id/departs"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignLeft="@+id/Horaire"
    android:layout_alignRight="@+id/Horaire"
    android:layout_below="@+id/Horaire"
    android:layout_marginTop="22dp"
    android:text="TextView" />

<ListView
    android:id="@+id/listView"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_below="@+id/departs"
    android:layout_centerHorizontal="true" >
</ListView>

</RelativeLayout>

最后“simplerow.xml”：

<?xml version="1.0" encoding="utf-8"?>
<TextView xmlns:android="http://schemas.android.com/apk/res/android"  
 android:id="@+id/rowTextView"   
 android:layout_width="fill_parent"   
 android:layout_height="wrap_content"  
 android:padding="10dp"  
 android:textSize="16sp" >  
</TextView>

Answer 1

您需要在setAdapter

上调用list2

 public ThreadStopName(ListView list, Activity context) {
    this.list2 = list;
    this.context = context;
 }

listView.setAdapter(arrayAdapter); should be changed

Listview - java.lang.NullPointerException

1 个答案: